Cyclone separator with enlarged underflow section

ABSTRACT

A cyclone separator with an inlet and two outlets for separating oil and water from an oil-water mixture wherein the separation chamber has a large diameter inlet end and a smaller diameter underflow outlet end. The overflow is arranged as an axial outlet at the inlet end of the chamber. The underflow outlet end is provided with a cone shaped portion of increasing diameter in the direction of flow and a choke portion downstream of the cone shaped portion, the choke having a reducing diameter configuration.

BACKGROUND OF THE INVENTION

This invention relates to cyclone separators.

The invention has particular, but not exclusive, application inliquid-separators, particularly separators for separating oil and waterfrom an oil-water mixture such as of the kind described in InternationalApplication No. PCT/AU83/00028, U.S. Pat. No. 4,464,264, U.S. Pat. No.4,576,724 or U.S. Pat. No. 4,237,006.

SUMMARY OF THE INVENTION

According to the invention there is provided a cyclone separator havingan elongate separating chamber extending from a larger diameter end to asmaller diameter end, and having an overflow outlet at the largerdiameter end, an underflow outlet at the smaller diameter end and inletmeans, for inlet of fluid to be separated to the separating chamber, ata lengthwise location at least adjacent the larger diameter end; whereinthe underflow outlet leads to an axially extending end portion of theseparator, through which, in use of the separator, outflow from theunderflow outlet passes, said end portion extending from a smallerdiameter end to a larger diameter end, the smaller diameter end of theend portion being closest to the larger diameter end of the separatingchamber. Preferably, said end portion is of frustoconical form withconicity (half-angle) in the range 6° to 20°, preferably 8°. Arestrictive choke may be provided downstream of the end portion and isin a generally frustoconical form decreasing in diameter away from theend portion.

BRIEF DESCRIPTION OF THE DRAWING

The invention is further described by way of example only with referenceto the accompanying drawing, the single FIGURE of which is a crosssectional diagram of a cyclone separator constructed in accordance withthe invention.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS

The exemplary cyclone separator shown comprises an outer casing 24 whichdefines an elongate separating chamber 24a therewithin. The separatingchamber is axially symmetrical and of circular transverse cross section.Chamber 24a extends from a larger diameter end 10a of the separator to asmaller diameter end 10b of the separator. In this instance, theseparating chamber defines a first portion 12 of cylindrical form, asecond tapered portion 14, which tapered portion 14 in turn leads to athird portion 16 of cylindrical form. A tapered portion 12a extendsbetween portions 12, 14. Portion 16 presents, at its end remote fromportion 12, an underflow outlet 23. The portion 16 thence leads to anend portion 18 of the separator. The separating chamber 24a has anunderflow outlet 23, for the denser fluid, this being located at the endof portion 16 remote from the larger diameter end 10a of the separator.The separating chamber 24a also has one or more tangential fluid inlets26 positioned adjacent the larger diameter end of the separator and anaxial overflow outlet 34 arranged at the larger diameter end (foroutflow of the less dense of the components of the fluid to beseparated)

The separator 10 is designed specifically, in this particular instance,for separation of oil from an oil-water mixture, the mixture beingadmitted via inlets 26, the separated water being taken off via outlet23 and the separated oil being taken off via outlet 34. Separators ofthis or other type suitable for separating liquid components one fromthe other are generally designed to ensure relatively low shear stresswithin the liquid as it is moving within the separating chamber 24a.International Application PCT/AU83/00028, U.S. Pat. No. 4,464,264,Australian patent specification No. 84713/82 and U.S. Pat. No. 4,237,006describe cyclone separators effective for separating oil from an oilywater mixture where water predominates. These disclose particularconfigurations and dimensional constraints applicable to this type ofseparator. Generally these separators are characterized by havingrelatively long length to diameter ratio, for example the diameter d₁ atthe larger diameter end of the separator may be related to the overalllength of the separator so that the overall length "L" is at least fivetimes the diameter d₁. More particularly, the separator may becharacterised by the following:

    10≦1.sub.2 /d.sub.2 ≦25

    0.04≦4A.sub.i /πd.sub.1.sup.2 ≦0.10

    d.sub.O d.sub.2 <0.25

    d.sub.1 >d.sub.2

d₂ >d₃, where d₁, d₂, d₃ and 1₁, 1₂, 1₃ are the diameters and lengths ofthe first portion 12, second portion 14 and third portion 16,respectively, A_(i) is the total cross sectional area of the or of allof the inlets 26 measured at the points of entry normal to the inletflow, and d_(O) is the diameter of the outlet 34.

Where provided, the tapered portion 12a may have a taper whose conicity(half-angle) is 10°. The portion 14 may have a taper whose conicity(half-angle) is 20' to 1°. Where a portion such as portion 14 istapered, the respective diameter such as diameter d₂ thereof in theabove formulae is to be taken as the diameter thereof at the largestdiameter end. These ratios are described in U.S. Pat. Nos. 4,576,724 and4,237,006. In a particular form, disclosed in U.S. Pat. No. 4,576,724,the following relationship applies:

    d.sub.0 d.sub.2 <0.1.

The portion 18 is of frustoconical form increasing, away from the outlet23 from a diameter d₃ at the end closest the outlet 23 to a diameter d₄at the end remote therefrom. The conicity (half-angle) "A" of theportion 18 may be 8° and portion 18 may be of length 1₄ rather more thanthe smallest diameter d₃ thereof such as 1<1₄ /d₃ <5. In accordance withconventional practice, the outlet 23 may be coupled such as via a pipe20 through a suitable flow restricting means, or choke 22, which may beconstructed in accordance with the teachings of U.S. Pat. specificationNo. 4,464,264, or International Application PCT/AU83/00028 for outflowtherefrom of the denser liquid (water in this instance) from theseparator. Particularly, the flow restricting means may present apassageway 22a which is of generally frustoconical form decreasing indiameter away from the end portion 18 to a diameter at the end remotefrom the end portion 18 which is in the range 1/3 to 2/3 the diameter ofthe passageway 22a at the end adjacent end portion 18.

The provision of the portion 18 has been found to be particularly usefulin that it permits a relative shortening of the length of the separatoras compared with its diameter, as compared with what would be the caseotherwise. As mentioned, separators for separating liquid components,particularly the aforementioned oily water mixtures, are generallycharacterized by being of relatively great length and the reduction inlength achievable by use of the portion 18 is therefore of practicalsignificance in enabling fitment of separators into confined spaces and,furthermore, in reducing manufacturing costs. The provision of theportion 18 is thought to facilitate operation by permitting recovery ofa dynamic pressure head loss which normally occurs in the operation ofseparators of the kind in question. In particular, there will normallybe a substantial static pressure loss from the inlets 26 to the outlet23 of the separator, and the frustoconical configuration of the portion18 aids in minimising this loss.

As described in International Application PCT/AU85/00010, the multipletangential inlets 26 shown may be replaced by a single inlet of involuteform.

I claim:
 1. A cyclone separator comprising elements designed, sized andarranged for treating an oil-water mixture for separating the more densewater component from the less dense oil component thereof, saidseparator having an elongate separating chamber including a taperedportion extending from a larger diameter end to a smaller diameter end,and having an overflow outlet at the larger diameter end, an underflowoutlet at the smaller diameter end and having a substantiallycylindrical portion adjacent the smaller diameter end and extendingdownstream thereof, and inlet means for inlet of fluid to be separatedto the separating chamber at a lengthwise location adjacent the largerdiameter end; wherein the underflow outlet leads to an axially extendingend portion of the separator, through which in use of the separator,outflow from the underflow outlet passes, said end portion extendingfrom a smaller diameter end to a larger diameter end, the smallerdiameter end of the end portion being closest to the larger diameter endof the separating chamber, and further wherein said separating chambercomprises first, second and third chamber portions axially arranged inthat order, the inlet means comprising at least one inlet open to thefirst portion, the overflow outlet and underflow outlet being arrangedto axially outlet from the first portion and the third portionrespectively, and wherein the first and third portions are ofsubstantially cylindrical form and the second portion is the taperedportion extending from a larger diameter end to a smaller diameter end,where 1₁, 1₂ and 1₃ are the lengths of the first, second, and thirdportions respectively, where d₁ is the diameter of the first portion 1₁and d₂ is the diameter at the largest end of the second portion 1₂, andwhere d₁ is greater than d₂ to form a tapering transition portionbetween the first portion and the second portion.
 2. A cyclone separatoras claimed in claim 1 wherein said end portion is of frustoconical form,with a conicity (half-angle) in the range of 6° to 20°.
 3. A cycloneseparator as claimed in claim 2 wherein the conicity (half-angle) of theend portion is substantially 8°.
 4. A cyclone separator as claimed inclaim 2 wherein the end portion is longer than the diameter thereof atthe smallest diameter end of the end portion.
 5. A cyclone separator asclaimed in claim 4 wherein

    1<1.sub.4 /d.sub.3 <5,

where 1₄ is the length of the end portion and d₃ is the diameter of theend portion at its smallest diameter end.
 6. A cyclone separator asclaimed in claim 1 including flow restriction means coupled to thelarger diameter end of said end portion to restrict flow from the endportion.
 7. A cyclone separator as claimed in claim 6 wherein said flowrestricting means comprises a passageway having a portion whichdecreases in diameter away from said end portion to a diameter at theend of the passageway portion remote from said end portion which is inthe range 1/3 to 2/3 of the diameter of the passageway adjacent said endportion.
 8. A cyclone separator comprising elements designed, sized andarranged for treating an oil-water mixture for separating the more densewater component from the less dense oil component thereof, saidseparator having an elongate separating chamber with a tapered portionextending from a larger diameter end to a smaller diameter end, andhaving an overflow outlet at the larger diameter end, an underflowoutlet at the smaller diameter end and having a substantiallycylindrical portion adjacent the smaller diameter end and extendingdownstream thereof, and inlet means for inlet of fluid to be separatedto the separating chamber at a lengthwise location adjacent the largerdiameter end, wherein the underflow outlet leads to an axially extendingend portion of the separator, through which in use of the separator,outflow from the underflow outlet passes, said end portion extendingfrom a smaller diameter end to a larger diameter end, the smallerdiameter end of the end portion being closest to the larger diameter endof the separating chamber, wherein said separating chamber comprisesfirst, second and third chamber portions axially arranged in that order,the inlet means comprising at least one inlet open to the first portion,the overflow outlet and underflow outlet being arranged to axiallyoutlet from the first portion and the third portion respectively, andwherein the first and third portions are of substantially cylindricalform and the second portion is said tapered portion, wherein

    10≦1.sub.2 /d.sub.2 ≦25

    0.04≦4A.sub.i /πd.sub.1.sup.2 ≦0.10

    d.sub.0 d.sub.2 <0.25

    d.sub.1 >d.sub.2

    d.sub.2 >d.sub.3

where 1₁, 1₂ and 1₃ are the lengths of the first, second and thirdportions respectively, d₁ and d₃ are the diameters of the first andthird portions respectively, d₂ is the diameter of the second portion atits largest diameter end, d₀ is the diameter of the overflow outlet andA_(i) is the total cross-sectional area for inflow of material to theseparating chamber as presented by the inlet means and measured at thepoints of entry normal to inlet flow.
 9. A cyclone separator as claimedn claim 8 including a tapered portion of the separating chamber, joiningsaid first and second portions thereof.
 10. A cyclone separator asclaimed in claim 8 wherein the conicity (half-angle) of the secondportion is in the range 20' to 1°.
 11. A cyclone separator as claimed inclaim 8 wherein d₀ d₂ <0.1.
 12. A cyclone separator having elementsdesigned, sized, and arranged for treating an oil-water mixture forseparating the more dense water component from the less dense oilcomponent thereof, said separator having an elongated separation chamberwith a tapered portion extending from a larger diameter end to a smallerdiameter end, an overflow outlet at the larger diameter end foroutflowing the less dense oil component of the mixture, an underflowoutlet for outflowing the more dense water component of the mixture andinlet means for inlet of the fluid mixture to be separated, suchseparating chamber having a relatively long length to diameter ratio andbeing arranged to provide a low shear stress to liquids moving withinthe separating chamber, and further wherein said separating chambercomprises first, second and third chamber portions axially arranged inthat order, the inlet means comprising at least one inlet open to thefirst portion, the overflow outlet and underflow outlet being arrangedto axially outlet from the first portion and the third portionrespectively, and wherein the first and third portions are ofsubstantially cylindrical form and the second portion is the taperedportion extending from a larger diameter end to a smaller diameter end,where 1₁, 1₂ and 1₃ are the lengths of the first, second, and thirdportions respectively, where d₁ is the diameter of the first portion 1₁and d₂ is the diameter at the largest end of the second portion 1₂, andwhere d₁ is greater than d₂ to form a tapering transition portionbetween the first portion and the second portion, andend portion meansarranged to extend from said third portion of said separation chamber atthe smaller diameter end thereof for minimizing pressure head lossoccurring in the separation process from the inlet to the underflowoutlet of the separation chamber, said end portion means beingfrustoconically shaped and expanding in diameter as it extends away fromsaid third portion of said separation chamber.
 13. The cyclone separatorof claim 12 and further including choke means on the water componentoutlet which is arranged downstream of said end portion means.
 14. Thecyclone separator of claim 13 wherein said choke means is of afrustoconical shape with the diameter of said choke means decreasing asit extends away from said end portion means.